Html helper to route back from a subdomain

I have created an mvc3 application that allows my customers to have there own subdomain page with the application e.g. www.subdomain.mydomain.com

The problem I am now facing is the main menu and footer that is contained within my _Layout meaning if a user browses to the subdomain my links are been rendered as www.subdomain.mydomain.com/about - www.subdomain.mydomain.com/contactus etc etc.

I assume I need to create a helper to enable m开发者_开发技巧apping the links back away from the subdomain but I dont have a clue where to start.....can anyone point me in the right direction?

Thank you

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I would suggest creating a _SubdomainLayout page, and set the links on that page to the URL you want.